Test 19 - Check Ignition Spark - Generac Power Systems GP Series Diagnostic Repair Manual

Section 4 Engine Diagnostic Tests
Set a DMM to measure DC voltage (12 VDC). Connect
meter positive (+) test lead to starter contactor stud (the
small jumper wire connected to starter). Connect
common (-) test lead to starter motor frame.
Set Start-Stop Switch to START and observe meter.
Meter should indicate battery voltage. Starter motor
should operate and engine should crank.
Results
If battery voltage is indicated on meter but motor
1.
did NOT operate, remove and test starter motor for
proper operation independent of engine.
If battery voltage was indicated and Starter Motor
2.
tried to engage (pinion engaged) but engine did not
crank, check for mechanical binding of engine or
rotor.
NOTE: If a starting problem is encountered, the engine
itself should be thoroughly checked to eliminate it as the
cause of starting difficulty. It is good practice to check
engine for freedom of rotation by removing spark plugs
and turning crankshaft over slowly by hand to be sure it
rotates freely.
IMPORTANT NOTE: Do not rotate engine with electric
starter with spark plugs removed. Arcing at the spark
plug ends may ignite the gasoline vapor exiting the spark
plug hole.
DANGER
Explosion and Fire. Fuel and vapors are extremely
flammable and explosive. Store fuel in a well
ventilated area. Keep fire and spark away. Failure to
do so will result in death or serious injury.
WARNING
Explosion. Turn fuel supply OFF before
checking for spark. Failure to do so could
result in death or severe injury.
Checking The Pinion
See Figure 4-8. When starter motor is activated, the
pinion gear should move and engage flywheel ring gear.
If pinion does not move normally, inspect pinion for
binding or sticking.
Figure 4-8. Check Pinion Gear Operation
28
Test 19 – Check Ignition Spark
Procedure
A commercially available spark tester may be used to
test engine ignition system. One can also be purchased
from Generac or local supplier.
Disconnect spark plug lead from spark plug.
1.
Attach high tension lead to spark tester terminal.
2.
See
3.
tester clamp by attaching to cylinder head.
Crank engine rapidly. Engine must crank at 350
4.
rpm or more. If spark jumps tester gap, assume the
ignition system is working properly. Repeat on
remaining cylinder spark plug.
(000143)
Figure 4-10. Testing Ignition System
(000333)
Figure 4-11. Checking Engine Misfire
If spark jumps tester gap intermittently, the problem
5.
may be in the ignition magneto.
Results
Refer to flow chart.
002403
Figure 4-9. Spark Tester
Figure 4-10 and Figure
Diagnostic Repair Manual
002415a
4-11. Ground spark